#! /usr/bin/perl
=head1 NAME

obj2opengl - converts obj files to arrays for glDrawArrays
=head1 SYNOPSIS

obj2opengl [options] file

use -help or -man for further information

=head1 DESCRIPTION

This script expects and OBJ file consisting of vertices,
texture coords and normals. Each face must contain
exactly 3 vertices. The texture coords are two dimonsional.

The resulting .H file offers three float arrays to be rendered
with glDrawArrays.

=head1 AUTHOR

Heiko Behrens (http://www.HeikoBehrens.net)

=head1 VERSION

25th August 2009 (initial version)

=head1 COPYRIGHT

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.

=head1 ACKNOWLEDGEMENTS

This script is based on the work of Margaret Geroch.

=head1 REQUIRED ARGUMENTS

The first or the last argument has to be an OBJ file according
to this () specification.

=head1 OPTIONS

=over

=item B<-help>

Print a brief help message and exits.

=item B<-man>

Prints the extended manual page and exits.

=item B<-noScale>

Prevents automatic scaling. Otherwise the object will be scaled
such the the longest dimension is 1 unit.

=item B<-scale <float>>

Sets the scale factor explicitly. Please be aware that negative numbers
are not handled correctly regarding the orientation of the normals.

=item B<-noMove>

Prevents automatic scaling. Otherwise the object will be moved to the center of
its vertices.

=item B<-o>, B<-outputFilename>

Name of the output file name. If omitted, the output file the same as the
input filename but with the extension .h

=item B<-nameOfObject>

Specifies the name of the generated variables. If omitted, same as
output filename without path and extension.

=item B<-noverbose>

Runs this script silently.
=cut

use Getopt::Long;
use File::Basename;
use Pod::Usage;

# -----------------------------------------------------------------
# Main Program
# -----------------------------------------------------------------
handleArguments();

# derive center coords and scale factor if neither provided nor disabled
unless(defined($scalefac) && defined($xcen)) {
calcSizeAndCenter();
}

if($verbose) {
printInputAndOptions();
}

# TODO check integrity: Does every referenced vertex, normal and coord exist?
loadData();
normalizeNormals();

if($verbose) {
printStatistics();
}

writeOutput();

# -----------------------------------------------------------------
# Sub Routines
# -----------------------------------------------------------------

sub handleArguments() {
my $help = 0;
my $man = 0;
my $noscale = 0;
my $nomove = 0;
$verbose = 1;
$errorInOptions = !GetOptions (
"help" => \$help,
"man" => \$man,
"noScale" => \$noscale,
"scale=f" => \$scalefac,
"noMove" => \$nomove,
"center=f{3}" => \@center,
"outputFilename=s" => \$outFilename,
"nameOfObject=s" => \$object,
"verbose!" => \$verbose,
);

if($noscale) {
$scalefac = 1;
}

if($nomove) {
@center = (0, 0, 0);
}

if(defined(@center)) {
$xcen = $center[0];
$ycen = $center[1];
$zcen = $center[2];
}

if($#ARGV == 0) {
my ($file, $dir, $ext) = fileparse($ARGV[0], qr/\.[^.]*/);
$inFilename = $dir . $file . $ext;
} else {
$errorInOptions = true;
}

# (optional) derive output filename from input filename
unless($errorInOptions || defined($outFilename)) {
my ($file, $dir, $ext) = fileparse($inFilename, qr/\.[^.]*/);
$outFilename = $dir . $file . ".h";
}

# (optional) define object name from output filename
unless($errorInOptions || defined($object)) {
my ($file, $dir, $ext) = fileparse($outFilename, qr/\.[^.]*/);
$object = $file;
}

($inFilename ne $outFilename) or
die ("Input filename must not be the same as output filename")
unless($errorInOptions);

if($errorInOptions || $man || $help) {
pod2usage(-verbose => 2) if $man;
pod2usage(-verbose => 1) if $help;
pod2usage();
}

# check wheter file exists
open ( INFILE, "<$inFilename" )
|| die "Can't find file '$inFilename' ...exiting \n";
close(INFILE);
}

# Stores center of object in $xcen, $ycen, $zcen
# and calculates scaling factor $scalefac to limit max
# side of object to 1.0 units
sub calcSizeAndCenter() {
open ( INFILE, "<$inFilename" )
|| die "Can't find file $inFilename...exiting \n";

$numVerts = 0;

my (
$xsum, $ysum, $zsum,
$xmin, $ymin, $zmin,
$xmax, $ymax, $zmax,
);

while ( $line = <INFILE> )
{
chop $line;

if ($line =~ /v\s+.*/)
{

$numVerts++;
@tokens = split(' ', $line);

$xsum += $tokens[1];
$ysum += $tokens[2];
$zsum += $tokens[3];

if ( $numVerts == 1 )
{
$xmin = $tokens[1];
$xmax = $tokens[1];
$ymin = $tokens[2];
$ymax = $tokens[2];
$zmin = $tokens[3];
$zmax = $tokens[3];
}
else
{
if ($tokens[1] < $xmin)
{
$xmin = $tokens[1];
}
elsif ($tokens[1] > $xmax)
{
$xmax = $tokens[1];
}

if ($tokens[2] < $ymin)
{
$ymin = $tokens[2];
}
elsif ($tokens[2] > $ymax)
{
$ymax = $tokens[2];
}

if ($tokens[3] < $zmin)
{
$zmin = $tokens[3];
}
elsif ($tokens[3] > $zmax)
{
$zmax = $tokens[3];
}

}

}

}
close INFILE;

# Calculate the center
unless(defined($xcen)) {
$xcen = $xsum / $numVerts;
$ycen = $ysum / $numVerts;
$zcen = $zsum / $numVerts;
}

# Calculate the scale factor
unless(defined($scalefac)) {
my $xdiff = ($xmax - $xmin);
my $ydiff = ($ymax - $ymin);
my $zdiff = ($zmax - $zmin);

if ( ( $xdiff >= $ydiff ) && ( $xdiff >= $zdiff ) )
{
$scalefac = $xdiff;
}
elsif ( ( $ydiff >= $xdiff ) && ( $ydiff >= $zdiff ) )
{
$scalefac = $ydiff;
}
else
{
$scalefac = $zdiff;
}
$scalefac = 1.0 / $scalefac;
}
}

sub printInputAndOptions() {
print "Input file : $inFilename\n";
print "Output file : $outFilename\n";
print "Object name : $object\n";
print "Center : <$xcen, $ycen, $zcen>\n";
print "Scale by : $scalefac\n";
}

sub printStatistics() {
print "----------------\n";
print "Vertices : $numVerts\n";
print "Faces : $numFaces\n";
print "Texture Coords : $numTexture\n";
print "Normals : $numNormals\n";
}

# reads vertices into $xcoords[], $ycoords[], $zcoords[]
# where coordinates are moved and scaled according to
# $xcen, $ycen, $zcen and $scalefac
# reads texture coords into $tx[], $ty[]
# where y coordinate is mirrowed
# reads normals into $nx[], $ny[], $nz[]
# but does not normalize, see normalizeNormals()
# reads faces and establishes lookup data where
# va_idx[], vb_idx[], vc_idx[] for vertices
# ta_idx[], tb_idx[], tc_idx[] for texture coords
# na_idx[], nb_idx[], nc_idx[] for normals
# store indizes for the former arrays respectively
# also, $face_line[] store actual face string
sub loadData {
$numVerts = 0;
$numFaces = 0;
$numTexture = 0;
$numNormals = 0;

open ( INFILE, "<$inFilename" )
|| die "Can't find file $inFilename...exiting \n";

while ($line = <INFILE>)
{
chop $line;

# vertices
if ($line =~ /v\s+.*/)
{
@tokens= split(' ', $line);
$x = ( $tokens[1] - $xcen ) * $scalefac;
$y = ( $tokens[2] - $ycen ) * $scalefac;
$z = ( $tokens[3] - $zcen ) * $scalefac;
$xcoords[$numVerts] = $x;
$ycoords[$numVerts] = $y;
$zcoords[$numVerts] = $z;

$numVerts++;
}

# texture coords
if ($line =~ /vt\s+.*/)
{
@tokens= split(' ', $line);
$x = $tokens[1];
$y = 1 - $tokens[2];
$tx[$numTexture] = $x;
$ty[$numTexture] = $y;

$numTexture++;
}

#normals
if ($line =~ /vn\s+.*/)
{
@tokens= split(' ', $line);
$x = $tokens[1];
$y = $tokens[2];
$z = $tokens[3];
$nx[$numNormals] = $x;
$ny[$numNormals] = $y;
$nz[$numNormals] = $z;

$numNormals++;
}

# faces
if ($line =~ /f\s+([^ ]+)\s+([^ ]+)\s+([^ ]+)/)
{
@a = split('/', $1);
@b = split('/', $2);
@c = split('/', $3);
$va_idx[$numFaces] = $a[0]-1;
$ta_idx[$numFaces] = $a[1]-1;
$na_idx[$numFaces] = $a[2]-1;

$vb_idx[$numFaces] = $b[0]-1;
$tb_idx[$numFaces] = $b[1]-1;
$nb_idx[$numFaces] = $b[2]-1;

$vc_idx[$numFaces] = $c[0]-1;
$tc_idx[$numFaces] = $c[1]-1;
$nc_idx[$numFaces] = $c[2]-1;

$face_line[$numFaces] = $line;

$numFaces++;
}
}

close INFILE;
}

sub normalizeNormals {
for ( $j = 0; $j < $numNormals; ++$j)
{
$d = sqrt ( $nx[$j]*$nx[$j] + $ny[$j]*$ny[$j] + $nz[$j]*$nz[$j] );

if ( $d == 0 )
{
$nx[$j] = 1;
$ny[$j] = 0;
$nz[$j] = 0;
}
else
{
$nx[$j] = $nx[$j] / $d;
$ny[$j] = $ny[$j] / $d;
$nz[$j] = $nz[$j] / $d;
}

}
}

sub writeOutput {
open ( OUTFILE, ">$outFilename" )
|| die "Can't create file $outFilename ... exiting\n";

print OUTFILE "/*\n";
print OUTFILE "created with obj2opengl.pl\n\n";

# some statistics
print OUTFILE "source file : $inFilename\n";
print OUTFILE "vertices : $numVerts\n";
print OUTFILE "faces : $numFaces\n";
print OUTFILE "normals : $numNormals\n";
print OUTFILE "texture coords : $numTexture\n";
print OUTFILE "\n\n";

# example usage
print OUTFILE "// include generated arrays\n";
print OUTFILE "#import \"".$outFilename."\"\n";
print OUTFILE "\n";
print OUTFILE "// set input data to arrays\n";
print OUTFILE "glVertexPointer(3, GL_FLOAT, 0, ".$object."Verts);\n";
print OUTFILE "glNormalPointer(GL_FLOAT, 0, ".$object."Normals);\n"
if $numNormals > 0;
print OUTFILE "glTexCoordPointer(2, GL_FLOAT, 0, ".$object."TexCoords);\n"
if $numTexture > 0;
print OUTFILE "\n";
print OUTFILE "// draw data\n";
print OUTFILE "glDrawArrays(GL_TRIANGLES, 0, ".$object."NumVerts);\n";
print OUTFILE "*/\n\n";

# needed constant for glDrawArrays
print OUTFILE "unsigned int ".$object."NumVerts = ".($numFaces * 3).";\n\n";

# write verts
print OUTFILE "float ".$object."Verts \[\] = {\n";
for( $j = 0; $j < $numFaces; $j++)
{
$ia = $va_idx[$j];
$ib = $vb_idx[$j];
$ic = $vc_idx[$j];
print OUTFILE " // $face_line[$j]\n";
print OUTFILE " $xcoords[$ia], $ycoords[$ia], $zcoords[$ia],\n";
print OUTFILE " $xcoords[$ib], $ycoords[$ib], $zcoords[$ib],\n";
print OUTFILE " $xcoords[$ic], $ycoords[$ic], $zcoords[$ic],\n";
}
print OUTFILE "};\n\n";

# write normals
if($numNormals > 0) {
print OUTFILE "float ".$object."Normals \[\] = {\n";
for( $j = 0; $j < $numFaces; $j++) {
$ia = $na_idx[$j];
$ib = $nb_idx[$j];
$ic = $nc_idx[$j];
print OUTFILE " // $face_line[$j]\n";
print OUTFILE " $nx[$ia], $ny[$ia], $nz[$ia],\n";
print OUTFILE " $nx[$ib], $ny[$ib], $nz[$ib],\n";
print OUTFILE " $nx[$ic], $ny[$ic], $nz[$ic],\n";
}

print OUTFILE "};\n\n";
}

# write texture coords
if($numTexture) {
print OUTFILE "float ".$object."TexCoords \[\] = {\n";
for( $j = 0; $j < $numFaces; $j++) {
$ia = $ta_idx[$j];
$ib = $tb_idx[$j];
$ic = $tc_idx[$j];
print OUTFILE " // $face_line[$j]\n";
print OUTFILE " $tx[$ia], $ty[$ia],\n";
print OUTFILE " $tx[$ib], $ty[$ib],\n";
print OUTFILE " $tx[$ic], $ty[$ic],\n";
}

print OUTFILE "};\n\n";
}

close OUTFILE;
}


